You're right, those games are priced differently, especially the #1 seller for the week which was 50% off during the sale. That just shows more clearly that discounts can lead to more profit by way of volume, as it tops full-priced games like Borderlands 2 and Black Ops 2. Or that really good, budget-priced indie titles (Torchlight 2) can hold their own when it comes to raking in the green.

Again, we list the source here, which explicitly states:

The top selling games on Steam by REVENUE for the week, updated every Sunday